The present invention relates to a component having a micromechanical microphone structure. The microphone structure includes an acoustically active diaphragm, which functions as deflectable electrode of a microphone capacitor, a stationary, acoustically permeable counter element, which functions as counter electrode of the microphone capacitor, and means for detecting and analyzing the capacitance changes of the microphone capacitor. The diaphragm is realized in a diaphragm layer above the semiconductor substrate of the component and spans a sound opening in the substrate rear. The counter element is developed in an additional layer above the diaphragm.
Furthermore, the present invention relates to a method for producing such components in the wafer composite and subsequent dice-up operation.
U.S. Patent Application Publication No. 2002/0067663 A1 describes a microphone component whose micromechanical microphone structure is realized in a layer structure above a semiconductor substrate. In this case, the perforated counter element forms a pedestal-type projection in the component surface, and its size is adapted to the diaphragm disposed underneath. This diaphragm spans a sound opening in the substrate rear. An air gap, which was produced by sacrificial-layer etching, is situated between the counter element and the diaphragm. The rigidity of the counter element of the conventional microphone component depends to a large extent on its circumferential shape, i.e., on the form of the pedestal edge region, by which the counter element is set apart from the diaphragm.
For cost-related reasons, the production of such microphone components mostly uses a wafer composite if at all possible. Toward this end, a multitude of microphone structures disposed in grid form is usually produced on a semiconductor wafer. Only then are the components diced up. The highly fragile structure of the conventional microphone component, which is sensitive to water, poses a problem in this context. The cost-efficient sawing with the aid of a water-cooled circular saw, which is very common in micro technology, cannot be used for these components without additional protective measures. It must be assumed that the sensitive microphone structures are unable to withstand the impinging water jet. In addition, water that penetrates the space between the two electrodes of the microphone capacitor leads to irreversible adhesion of the diaphragm to the counter element, which also destroys the microphone function.
For this reason, micromechanical microphone components of the type mentioned above are currently separated using special processes. Stealth dicing, in which rupture joints are produced in the wafer material, is used particularly often. The wafer is then broken into individual chips along these rupture joints, sometimes with the aid of a blade. This requires special machinery and thus additional investment expense. Furthermore, the process times for the generally utilized wafers having a thickness of 400 μm to 800 μm are relatively long, due to the high number of required “laser cuts”, among other things.